Base resistant fluorinated polymers

ABSTRACT

Disclosed herein are copolymers of tetrafluoroethylene and n-alkyl trifluorovinyl ether which further contain either curesite repeat units and/or iodine. Such curesite repeat units, upon exposure to free radicals, may crosslink the copolymers. The iodine is introduced by carrying out free radical polymerization in the presence of an organic iodide chain transfer agent. The polymers according to the invention are especially useful as elastomers and/or as molding resins for articles or parts that may be exposed to a basic environment. The preparation of such polymers by aqueous emulsion polymerization is also disclosed.

This application is a division of Ser. No. 08/973,382, Dec. 3, 1997,U.S. Pat. No. 5,852,150, Provisional Application No. 60/000,062, filedJun. 8, 1995.

FIELD OF THE INVENTION

Disclosed herein are polymers derived from tetrafluoroethylene, an alkyltrifluorovinyl ether, and a curesite monomer and/or an organic iodidecompound. A process for preparing such polymers is also disclosed. Suchpolymers are especially useful as base resistant elastomers.

TECHNICAL BACKGROUND

Fluoropolymers are generally well known for their chemical and thermalresistance. Partially fluorinated polymers, however, usually have someweakness towards certain types of chemicals, particularly bases. Suchpolymers often undergo dehydrofluorination or other reactions in thepresence of bases, making them unsuitable for use in basic environments.This is particularly true for partially fluorinated polymers which areelastomers, since they are often used as seals for systems which arebasic. For this reason, partially fluorinated polymers which arerelatively stable to bases have been sought.

U.S. Pat. No. 3,159,609 describes copolymers of tetrafluoroethylene(TFE) and alkyl trifluorovinyl ethers. These polymers are not describedas being readily crosslinkable.

U.S. Pat. Nos. 4,158,678, 4,243,770, 4,948,852 and 4,973,633 describethe use of organic iodides as chain transfer agent in fluoromonomerpolymerizations. None of these references teach the polymers of thisinvention.

SUMMARY OF THE INVENTION

This invention concerns a first polymer comprising the repeat units##STR1## and a crosslink-functional repeat unit (III), which enablessaid polymer to readily crosslink upon exposure of said polymer to freeradicals, wherein R¹ is an alkyl group containing 1 to 6 carbon atoms.Preferably, the molar ratio of (I):(II) is about 4:1 to about 1:1, andthe molar ratio of [(I)+(II)]:(III) is about 200:1 to about 20:1. Therepeat units (I)+(II)+(III) are, in combination, about 50 mole percentor more of the repeat units making up the polymer.

In the above formulas, the repeat unit (I) can be derived from themonomer tetrafluoroethylene (IV), and the repeat unit (II) can bederived from a monomer of the formula CF₂ ═CFOR³ (V).

A novel process for preparing the above-described polymer is alsodisclosed, which process comprises reacting an admixture of monomerscomprising at least 50 mole percent of a combination oftetrafluoroethylene, at least one monomer within the formula CF₂ ═CFOR¹,and at least one crosslink-functional comonomer, wherein thepolymerization process is carried out in an aqueous emulsion at atemperature of from about 30 to 80° C. at a tetrafluoroethylene pressureof about 1 to 6 MPa.

The present invention also concerns a second polymer, which is made byfree radically copolymerizing, in the presence of an organic iodide, thefollowing monomers: tetrafluoroethylene (IV), a compound of the formulaCF₂ ═CFOR¹ (V), wherein R¹ is alkyl containing 1 to 6 carbon atoms, and,optionally, other free radically copolymerizable monomers, such that thepolymer product contains about 0.1 to about 5 percent by weight ofiodine. The monomers (IV) and (V) react to form, respectively, repeatunits (I) and (II), as defined above, which repeat units, incombination, are at least 50 mole percent of the repeat units making upthe polymer product.

DETAILS OF THE INVENTION

The present invention includes two kinds of copolymers which are usefulas base resistant elastomers and which contain a repeat unit derivedfrom a trifluorovinyl ether monomer. The first polymer described hereinhas three necessary repeat units, herein labelled (I), (II) and (III).Unit (I) is derived from tetrafluoroethylene (TFE), while repeat unit(II) is derived from a trifluorovinyl ether monomer of the formula CF₂═CFOR¹ (V). The monomer from which repeat unit (II) is derived may bemade by the method described in U.S. Pat. No. 2,917,548, herebyincorporated by reference in its entirety. In a preferred embodiment, R¹in (II) and (V) are ethyl, n-propyl or n-butyl, more preferably n-butyl.

If a polymer consisted only of repeat units (I) and (II), it could onlybe free radically crosslinked with relative difficulty. Repeat unit(III) enables the polymer to be readily crosslinked when exposed to freeradicals (or sources of energy that create free radicals). The abilityto readily form crosslinks at a sufficiently high level or concentrationis important for elastomeric polymers, in order to provide goodvulcanizate properties.

In a preferred embodiment of the first kind of polymer according to thepresent invention, the polymer is an elastomer, i.e., a copolymer thatis above its glass transition temperature and contains no appreciableamount of crystallinity at 20° C., as measured by differential scanningcalorimetry.

Repeat units and monomers which readily enable crosslinking offluoropolymers under free radical conditions are well known. See, forinstance, U.S. Pat. Nos. 4,035,565, 4,564,662, 4,745,165, 4,694,045,4,948,852, 4,973,633 and 5,173,553, all of which are hereby incorporatedby reference in their entirety.

Crosslink-functional monomers which are adapted to provide a reactivecuresite for the polymer, include those that contain bromine in a sidechain. Suitable bromine-containing curesite monomers includebromotetrafluorobutene, bromotrifluoroethylene, and brominatedfluorovinyl ethers such as CF₂ ═CFOCF₂ CF₂ Br and CF₃ CH₂ OCF═CFBr.

Free-radical crosslinking sites may also be found on repeat units whichcontain alkyl groups having at least 1 methine hydrogen atom (a hydrogenatom bound to a carbon atom which in turn is bound to three other carbonatoms) in a side chain, or which contain an alkyl ether group in a sidechain, wherein the alkyl is substituted or unsubstituted. More than onerepeat unit (III) that promotes free radical crosslinking of the polymermay be present.

Preferred repeat units (III) are as follows: ##STR2## wherein i and k isan integer in the range of 2 to 10, preferably 2 or 4, j is an integerin the range of 1 to 4, preferably 1, and each R² is independently analkyl group containing 1 to 4 carbons. It is preferred if both R² groupsare methyl. The monomers for preferred repeat unit (IIIA) can be made bymethods described in P. Tarrant, et al., J. Org. Chem., vol. 34, p.864ff (1969). The monomers which polymerize to form the above repeatunits (IIIB) and (IIIC) can be made by the reaction of an alkoxide ofthe corresponding alcohol with tetrafluoroethylene, as will be readilyappreciated by the skilled artisan.

Preferably, in the above-described polymers, the molar ratio of (I):(II)is about 3:1 to about 13:7, and/or the molar ratio of [(I)+(II)]:(III)is about 130:1 to about 70:1.

In the first polymer according to the present invention, up to 50 molepercent of the repeat units may be units other than (I), (II), and(III). These other units may be derived from a wide variety of knownmonomers which free radically copolymerize with the monomers from whichrepeat units (I), (II) and (III) are derived. For examples of such knownmonomers, see, for instance, W. Gerhartz, et al., Ed., Ullmann'sEncyclopedia of Industrial Chemistry, vol. A11, at p. 393-429 (VCHVerlagsgesellschaft mbH, Weinheim 5th Ed. 1988); and H. F. Mark, et al.,Ed., Encyclopedia of Polymer Science and Technology, at p. 577-648 (JohnWiley & Sons, New York 3d Ed. 1989), of which the cited pages are herebyincorporated by reference. Accordingly, suitable optional comonomersinclude vinylidene fluoride, hexafluoropropylene, perfluoro(alkyl vinylether), preferably wherein the alkyl group contains 1 to 5 carbon atoms,especially perfluoro(methyl vinyl ether). Preferably, the optionalrepeat units are present in the first polymer in an amount of less than35 mole percent of the repeat units of the first polymer. Morepreferably, the first polymer consists essentially of repeat units (I),(II) and (III).

The first polymers according to the present invention may be prepared byfree radical polymerization using methods known to the skilled artisan.See, for instance, W. Gerhartz, et al., Ed., Ullmann's Encyclopedia ofIndustrial Chemistry, vol. A11, at p. 393-429 (VCH VerlagsgesellschaftmbH, Weinheim, 5th Ed. 1988); and H. F. Mark, et al., Ed., Encyclopediaof Polymer science and Technology, at 577-648 (John Wiley & Sons, NewYork 3d Ed. 1989). These polymers may be made by batch, semi-batch orcontinuous processes, employing solution, aqueous, non-aqueoussuspension, or emulsion polymerization processes. Such polymers shouldpreferably be of sufficient molecular weight so that a usefulcrosslinkable elastomer can be formed, although lower molecular weightsmay also be useful, for example, as crosslinkable caulks.

Preferably, the first or second polymers according to the presentinvention is made by an aqueous emulsion polymerization carried out atabout 30 to 80° C., preferably about 35 to 45° C., and most preferablyabout 40±5° C. in a semi-batch or continuous mode, at a TFE pressure ofabout 1-6 MPa, preferably 1-3 MPa. Such a polymerization is illustratedby Example 12 herein.

The first polymers according to the present invention may be in acrosslinked or uncrosslinked form. These polymers may be crosslinked bymixing them with a suitable amount of at least one free radicalgenerator, typically about 1 to about 10 weight percent of the generatorin the reaction mixture, and heating to generate free radicals and hencecrosslink. As the artisan will readily understand, free radicals shouldbe generated which are of sufficiently high energy to causecrosslinking. Suitable free radical generators include2,5-dimethyl-2,5-bis(t-butylperoxy)hexane (available asLupersol®/Luperco® 101XL from Atochem, Inc.),2,5-dimethyl-2,5-bis-t-butylperoxy)hex-3-yne (available asLupersol®/Luperco® 130XL from Atochem, Inc.), di-t-butyl peroxide, anddicumyl peroxide. Suitable coagents, such as triallyl isocyanurate ortrimethallyl isocyanurate, may also be used to improve the efficiency ofcrosslinking by the radical generator.

The second polymer of the present invention is a polymer which is madeby free radical polymerization of TFE (IV) and CF₂ ═CFOR¹ (V), whereinR¹ is an alkyl group containing 1 to 6 carbon atoms. In this case, R¹preferably contains 2 to 4 carbon atoms. It is also preferred that R¹ isn-alkyl. It is especially preferred that R¹ is n butyl. Thepolymerization to make the second polymer is carried out by essentiallythe same methods employed to prepare the first polymer disclosed herein(see above), except that an organic iodide must be present and themonomer for making repeat unit (III) may not necessarily be present.

The organic iodide acts as a chain transfer agent, thereby resulting iniodine atoms becoming part of the product polymer. The product polymercontains about 0.1 to about 5 weight percent of iodine, preferably about0.5 to about 2.5 weight percent of iodine. For listings of such iodides,and how such iodides are used, see U.S. Pat. Nos. 4,158,678, 4,243,770,4,948,852 and 4,973,633, which are hereby incorporated by reference.Preferred iodides are R⁴ I, wherein R⁴ is perfluoroalkyl, CH₂ I₂, andI(CH₂ CH₂)_(p) (CF₂)_(m) (CH₂ CH₂)_(p) I, wherein m is 1-10, preferably2, and each p is independently 0 or 1, preferably 0.

The weight percent of iodine in the polymer may be measured as describedin Analytical Chemistry, vol. 22, p. 1047ff (1950). The iodine analysesreported herein were done by Schwartzkopf Microanalytical Laboratoriesusing this method.

The second polymer according to the present invention is preferablyelastomeric. This second polymer may optionally contain up to 50 molepercent of repeat units derived from monomers other than TFE (IV) andCF₂ ═CFOR³ (V). The optional and preferred monomers listed above for thefirst polymer are also optional and preferred for the second polymer. Inaddition, any of the repeat units (III) mentioned above may be presentin the second polymer (as part of the optional repeat units). Thepreferred repeat units (III) mentioned above are also the preferredoptional repeat units in the second polymer.

The second polymer herein may be crosslinked or uncrosslinked. Thepolymer may be free radically crosslinked by methods described above forthe first polymer.

Polymers according to the present invention, of both the first andsecond kind described herein, are useful as elastomers and moldingresins for making parts which require heat and chemical, especiallybase, resistance. When used as thermoplastic molding resins, thepolymers may be crosslinked during molding by incorporating a freeradical generating agent that decomposes at the molding temperatures. Ifthe polymer is elastomeric, however, it is preferably crosslinkedduring, for example, molding or extrusion, as is done with mostelastomers. The resulting parts are useful, for example, in gaskets andseals, including o-rings, especially where chemical and temperatureresistance, particularly base resistance, is required. These polymersare especially useful when used in contact with certain basic fluids,such as monoamines and polyamines.

Except where noted, all pressures in the following Examples are gaugepressures. The following abbreviations are used in the Examples:

    ______________________________________                                        BTFB          4-bromo-3,3,4,4-tetrafluorobut-1-ene                            BuFVE         n-butyl trifluorovinyl ether                                    DSC           Differential Scanning Calorimetry                               TFE           tetrafluoroethylene                                             T.sub.g       glass transition temperature                                    TGA           ThermoGravimetric Analysis                                      ______________________________________                                    

EXAMPLE 1

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CH₂ ═CHCF₂ CF₂ Br in a 30:10:1 mole ratio in organicmedia. A 75 ml pressure vessel was charged with 7.7 g of CF₂ ═CF--O--C₄H₉, 1.04 g of CH₂ ═CHCF₂ CF₂ Br, 0.2 gbis(t-butylcyclohexyl)peroxy-dicarbonate and 40 g of1,1,2-trichlorotrifluoroethane. The vessel was sealed, cooled in dryice, evacuated and charged with about 15 g of CF₂ ═CF₂. The vessel wasthen heated to 60° C. for 12 hr with agitation. The internal pressurereached a maximum of about 1.89 MPa and fell to less than 345 kPa after5.6 hr. The vessel was cooled to 25° C. and vented to atmosphericpressure. A hazy fluid polymer solution was discharged. The volatilecomponents were evaporated under a heat lamp and then in a vacuum ovenat 100° C. to yield 22 g of a clear polymer which could be pressed at80° C. into a clear, flexible, tough film. DSC analysis showed a T_(g)at -19.1° C. on the second heat and no crystalline melting point. TGAanalysis showed a 10% weight loss at 316.7° C. in air and at 363.0° C.in nitrogen. The polymer was shown to contain 76.5 mole % CF₂ ═CF₂ and23.5 mole % CF₂ ═CF--O--C₄ H₉ by integration of the appropriateresonances in the ¹⁹ F nmr measured in tetrachloroethane at 140° C.Elemental analysis found the following: C, 30.93 wt %; H, 2.03 wt %; F,60.72 wt %; Br, 1.61 wt %, from which the composition 73.1 mole % CF₂═CF₂, 25.7 mole % CF₂ ═CF--O--C₄ H₉ and 1.1 mole % CH₂ ═CHCF₂ CF₂ Br wascalculated.

EXAMPLE 2

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CF₂ ═CF--O--CH₂ CH₂ OCH₃ in a 30:10:1 mole ratio inorganic media. A 75 ml pressure vessel was charged with 7.7 g of CF₂═CF--O--C₄ H₉, 0.78 g of CF₂ ═CF--O--CH₂ CH₂ OCH₃, 0.2 gbis(t-butylcyclohexyl)peroxydicarbonate and 40 g of1,1,2-trichlorotrifluoroethane. The vessel was sealed, cooled in dryice, evacuated and charged with about 15 g CF₂ ═CF₂. The vessel washeated to 60° C. for 12 hr with agitation. The internal pressure reacheda maximum of about 2.07 MPa and fell to less than 345 kPa after 7 hr.The vessel was cooled to 25° C. and vented to atmospheric pressure. Ahazy fluid containing chunks of gelatinous material was discharged. Thevolatile components were evaporated under a heat lamp and then in avacuum oven at 100° C. to yield 24.5 g of a clear polymer which could bepressed at 80° C. into a clear, flexible, tough film. DSC analysisshowed a T_(g) at -17.1° C. on the second heat and no crystallinemelting point. TGA analysis showed a 10% weight loss at 321.5° C., inair, and at 380.2° C., in nitrogen. The polymer was shown to contain 75mole % CF₂ ═CF₂ and 25 mole % combined CF₂ ═CF--O--C₄ H₉ and CF₂═CF--O--CH₂ CH₂ OCH₃ by integration of the appropriate resonances in the¹⁹ F nmr measured in tetrachloroethane at 140° C. The ratio of CF₂═CF--O--C₄ H₉ to CF₂ ═CF--O--CH₂ CH₂ OCH₃ was shown to be 13.6 to 1 byintegration of the --CH₃ resonance of CF₂ ═CF--O--C₄ H₉ at δ, 0.98 andthe --CH₃ resonance of CF₂ ═CF--O--CH₂ CH₂ OCH₃ at δ, 3.4 in the ¹ H nmrmeasured in tetrachloroethane at 130° C.

EXAMPLE 3

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CF₂ ═CF--O--CH₂ CH(CH₃)₂ in a 30:10:1 mole ratio inorganic media. A 75 ml pressure vessel was charged with 7.7 g of CF₂═CF--O--C₄ H₉, 0.77 g of CF₂ ═CF--O--CH₂ CH(CH₃)₂, 0.2 gbis(t-butylcyclohexyl)peroxydicarbonate and 40 g of1,1,2-trichlorotrifluoroethane. The vessel was sealed, cooled in dryice, evacuated and charged with about 15 g CF₂ ═CF₂. The vessel washeated to 60° C. for 12 hr with agitation. The internal pressure reacheda maximum of about 2.07 MPa and fell to less than 345 kPa after 6 hr.The vessel was cooled to 25° C. and vented to atmospheric pressure. Ahazy fluid containing chunks of gelatinous material was discharged. Thevolatile components were evaporated under a heat lamp and then in avacuum oven at 100° C. to yield 23.5 g of a clear polymer which could bepressed at 100° C. into a clear, flexible, tough film. DSC analysisshowed a T_(g) at -20.7° C. on the second heat and no crystallinemelting point. TGA analysis showed a 10% weight loss at 326.4° C. in airand at 378.8° C. in nitrogen. The polymer was shown to contain 75 mole %CF₂ ═CF₂ and 25 mole % combined CF₂ ═CF--O--C₄ H₉ and CF₂ ═CF--O--CH₂CH(CH₃)₂ by integration of the appropriate resonances in the ¹⁹ F nmrmeasured in tetrachloroethane at 150° C. The ratio of CF₂ ═CF--O--C₄ H₉to CF₂ ═CF--O--CH₂ CH(CH₃)₂ was shown to be 10 to 1 by integration ofthe --OCH₂ -- resonance of CF₂ ═CF--O--C₄ H₉ at δ, 4.06 and the --OCH₂-- resonance of CF₂ ═CF--O--CH₂ CH(CH₃)₂ at δ, 3.85 in the ¹ H nmrmeasured in tetrachloroethane at 130° C.

EXAMPLE 4

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CF₂ ═CF--O--(CH₂)₂ CH(CH₃)₂ in a 30:10:1 mole ratio inorganic media. A 75 ml pressure vessel was charged with 7.7 g of CF₂═CF--O--C₄ H₉, 0.84 g of CF₂ ═CF--O--(CH₂)₂ CH(CH₃)₂, 0.2 gbis(t-butylcyclohexyl)peroxydicarbonate and 40 g of1,1,2-trichlorotrifluoroethane. The vessel was sealed, cooled in dryice, evacuated and charged with about 15 g CF₂ ═CF₂. The vessel washeated to 60° C. for 12 hr with agitation. The internal pressure reacheda maximum of about 1.86 MPa and fell to less than 482 kPa after 12 hr.The vessel was cooled to 25° C. and vented to atmospheric pressure. Ahazy fluid of low viscosity was discharged. The volatile components wereevaporated under a heat lamp and then in a vacuum oven at 100° C. toyield 20.3 g of clear polymer which could be pressed at 80° C. into aclear, flexible film. DSC analysis showed a T_(g) at -17.4° C. on thesecond heat and no crystalline melting point. TGA analysis showed a 10%weight loss at 307.1° C. in air and at 351.6° C. in nitrogen. Thepolymer was shown to contain 73 mole % CF₂ ═CF₂ and 27 mole % combinedCF₂ ═CF--O--C₄ H₉ and CF₂ ═CF--O--(CH₂)₂ CH(CH₃)₂ by integration of theappropriate resonances in the ¹⁹ F nmr measured in tetrachloroethane at150° C. The ratio of CF₂ ═CF--O--C₄ H₉ to CF₂ ═CF--O--(CH₂)₂ CH(CH₃)₂was shown to be 8.6 to 1 by integration of the --OCH₂ -- resonance ofCF₂ ═C--O--C₄ H₉ at δ, 4.06 and the combined --CH₃ resonances of CF₂═CF--O--C₄ H₉ and CF₂ ═CF--O--(CH₂)₂ CH(CH₃)₂ at δ, 0.98 in the ¹ H nmrmeasured in tetrachloroethane at 130° C.

EXAMPLE 5

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and I--CF₂ CF₂ --I in a 30:10:1 mole ratio in organicmedia. A 75 ml pressure vessel was charged with 7.7 g of CF₂ ═CF--O--C₄H₉, 1.8 g of I--CF₂ CF₂ --I, 0.2 gbis(t-butylcyclohexyl)peroxydicarbonate and 40 g of1,1,2-trichlorotrifluoroethane. The vessel was sealed, cooled in dryice, evacuated and charged with about 15 g CF₂ ═CF₂. The vessel washeated to 60° C. for 12 hr with agitation. The internal pressure reacheda maximum of about 2.07 MPa and fell to less than 345 kPa after 10 hr.The vessel was cooled to 25° C. and vented to atmospheric pressure. Aclear polymer solution of low viscosity was discharged. The volatilecomponents were evaporated under a heat lamp and then in a vacuum ovenat 100° C. to yield 24.9 g of a clear polymer which could be pressed at60° C. into a clear, flexible film. DSC analysis showed a T_(g) at -29°C. on the second heat and no crystalline melting point. TGA analysisshowed a 10% weight loss at about 320° C. in air and at about 350° C. innitrogen. The polymer was shown to contain 79 mole % CF₂ ═CF₂ and 21mole % CF₂ ═CF--O--C₄ H₉ by integration of the appropriate resonances inthe ¹⁹ F nmr measured in tetrachloroethane at 140° C. Elemental analysisfound: C, 29.39 wt %; H, 1.90 wt %; F, 60.75 wt %; I, 4.70 wt %.

EXAMPLE 6

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and I--(CF₂ CF₂)₂ --I in a 30:10:1 mole ratio in organicmedia. A 75 ml pressure vessel was charged with 7.7 g of CF₂ ═CF--O--C₄H₉, 2.3 g of I--(CF₂ CF₂)₂ --I, 0.2 gbis(t-butylcyclohexyl)peroxydicarbonate and 40 g of1,1,2-trichlorotrifluoroethane. The vessel was sealed, cooled in dryice, evacuated and charged with about 15 g CF₂ ═CF₂. The vessel washeated to 60° C. for 12 hr with agitation. The internal pressure reacheda maximum of about 1.89 MPa and fell to less than 345 kPa after 6 hr.The vessel was cooled to 25° C. and vented to atmospheric pressure. Aclear polymer solution of low viscosity was discharged. The volatilecomponents were evaporated under a heat lamp and then in a vacuum ovenat 100° C. to yield 23.7 g of a clear polymer which could be pressed at60° C. into a slightly pink, flexible film. DSC analysis showed a T_(g)at -25.9° C. on the second heat and no crystalline melting point. TGAanalysis showed a 10% weight loss at about 299.5° C. in air and at about328.1° C. in nitrogen. The polymer was shown to contain 78 mole % CF₂═CF₂ and 22 mole % CF₂ ═CF--O--C₄ H₉ by integration of the appropriateresonances in the ¹⁹ F nmr measured in tetrachloroethane at 140° C.Elemental analysis found: C, 29.46 wt %; H, 1.90 wt %; F, 60.64 wt %; I,4.65 wt %.

EXAMPLE 7

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and I--CH₂ --I in a 75:25:1 mole ratio in organic media. A75 ml pressure vessel was charged with 7.7 g of CF₂ ═CF--O--C₄ H₉, 0.54g of I--CH₂ --I, 0.2 g bis(t-butylcyclohexyl)peroxydicarbonate and 40 gof 1,1,2-trichlorotrifluoroethane. The vessel was sealed, cooled in dryice, evacuated and charged with about 15 g CF₂ ═CF₂. The vessel washeated to 60° C. for 12 hr with agitation. The internal pressure reacheda maximum of about 2.00 MPa and fell to less than 345 kPa after 8 hr.The vessel was cooled to 25° C. and vented to atmospheric pressure. Ahazy polymer solution of low viscosity was discharged. The volatilecomponents were evaporated under a heat lamp and then in a vacuum ovenat 100° C. to yield 24.2 g of a clear polymer which could be pressed at80° C. into a clear, tough, flexible film. DSC analysis showed a T_(g)at -26.9° C. on the second heat and no crystalline melting point. TGAanalysis showed a 10% weight loss at about 325° C. in air and at about370° C. in nitrogen. The polymer was shown to contain 77 mole % CF₂ ═CF₂and 23 mole % CF₂ ═CF--O--C₄ H₉ by integration of the appropriateresonances in the ¹⁹ F nmr measured in tetrachloroethane at 140° C.Elemental analysis found: C, 30.0 wt %; H, 1.86 wt %; F, 60.56 wt %; I,0.96 wt %.

EXAMPLE 8

This example illustrates crosslinking polymers by action of an organicperoxide and radical trapping agent. Solutions of the polymers made inExamples 1-7 were prepared by dissolving 1 g of polymer, 0.03 g ofLupersol®-101 and 0.03 g of Diak®-7 (triallyl isocyanurate) in 5 ml ofhexafluorobenzene. The solutions were transferred to 10 ml glasspressure vessels. The vessels were cooled in liquid nitrogen, evacuatedand sealed. The reaction mixtures were defrosted and swirled until allcomponents were completely dissolved. The solutions were completelyfluid and of low viscosity. The vessels were heated in an uprightposition to 170° C. for 16-17 hr at which time they were cooled to 25°C. in an upright position. Upon inspection, the reaction mixtures hadall undergone crosslinking to polymer networks which turned the reactionmixtures from low-viscosity fluids to immobile gels.

EXAMPLE 9

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CH₂ ═CHCF₂ CF₂ Br in a 75:25:0.55 mole ratio inaqueous media at 80° C. A 1940 ml horizontal stainless-steel autoclaveequipped with a 4-bladed agitator was charged with 1100 ml deionizedwater and 16 g ammonium perfluorooctanoate. The autoclave was sealed,pressurized with nitrogen to 684 kPa and then vented to 0 kPa. Thispressure/venting cycle was repeated two times. The autoclave wasevacuated to 0 kPa (absolute) and then purged with CF₂ ═CF₂ (TFE) to 0kPa. This evacuation/purge cycle was repeated two times. At 0 kPa of TFEin the autoclave, 2 ml CF₂ ═CF--O--C₄ H₉ (BuFVE) and 2 ml CH₂ ═CHCF₂ CF₂Br (BTFB) were injected into the autoclave. The autoclave was agitatedat 150 rpm and heated to 80° C. and then charged with an additional 72 gTFE, 5.8 ml BuFVE and 0.5 ml BTFB (a 95:5:0.5 mole ratio). The pressurereached a maximum of about 2.07 MPa. Solution A, containing 1 g ammoniumpersulfate and 1 ml concentrated ammonium hydroxide per 100 ml deionizedwater, was injected at 10 ml/min for 20 ml and then continuously at 1ml/min. The polymerization initiated, a mixture of TFE, BuFVE and BTFBin a 75:25:0.55 mole ratio was fed to the autoclave at about the rate atwhich it was consumed, while maintaining about 2.07 MPa pressure in theautoclave. After the reaction had progressed for about 2.5 hr, the rateof injection of solution A was decreased to 0.75 ml/min. After thereaction had progressed for about 2.75 hr, the rate of injection ofsolution A was decreased to 0.5 ml/min. After the reaction hadprogressed for about 3 hr, the rate of injection of solution A wasdecreased to 0.25 ml/min. The reaction was continued until about 400 gof TFE and BuFVE were fed to the autoclave. The autoclave contents werecooled to ambient temperature, vented to 0 kPa and discharged as apolymer emulsion. The emulsion was poured into a rapidly stirredsolution of 50 g magnesium sulfate in 6 l deionized water at 25° C. toprecipitate the polymer. The polymer was filtered and washed six timeswith water at 25° C. and then dried at 80° C. under partial vacuum witha sweep of nitrogen to yield 367 g of a soft slightly tacky polymerwhich could be pressed into dense slabs at 90° C. DSC analysis showed aT_(g) at -3.6° C. on the second heat and no crystalline melting point.Elemental analysis found the following: C, 30.71 wt %; H, 1.96 wt %; F,63.15 wt %; Br, 1.04 wt % from which the composition 74.7 mole % CF₂═CF₂, 23.8 mole % CF₂ ═CF--O--C₄ H₉ and 1.5 mole % CH₂ ═CHCF₂ CF₂ Br wascalculated.

EXAMPLE 10

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CH₂ ═CHCF₂ CF₂ Br in a 70:30:0.67 mole ratio inaqueous media at 70° C. A 1940 ml horizontal stainless-steel autoclaveequipped with a 4-bladed agitator was charged with 1000 ml deionizedwater, 0.5 g sodium sulfite and 16 g ammonium perfluorooctanoate. Theautoclave was sealed, pressurized with nitrogen to 689 kPa and thenvented to 0 Pa. This pressure/venting cycle was repeated two times. Theautoclave was evacuated to 0 kPa (absolute) and then purged with CF₂═CF₂ (TFE) to 0 kPa. This evacuation/purge cycle was repeated two times.The autoclave was agitated at 150 rpm and heated to 70° C. and thencharged with an additional 93 g TFE, 6.8 ml BuFVE and 0.62 ml BTFB (a95:5:0.5 mole ratio). The pressure reached a maximum of about 2.07 MPa.Solution A, containing 2 g ammonium persulfate and 2 ml concentratedammonium hydroxide per 100 ml deionized water, was injected at 3 ml/minfor 15 ml. Concurrently, solution B, containing 2.2 g sodium sulfite per100 ml deionized water, was injected at 3 ml/min for 15 ml. Solutions Aand B were then each injected continuously at 0.5 ml/min. Thepolymerization initiated, a mixture of TFE, BuFVE and BTFB in a70:30:0.67 mole ratio was fed to the autoclave at about the rate atwhich it was consumed maintaining about 2.07 MPa pressure in theautoclave. After the reaction had progressed for about 2 hr, the ratesof injection of solutions A and B were each increased to 0.75 ml/min.After the reaction had progressed for about 3 hr, the rates of injectionof solutions A and B were each increased to 1.0 ml/min. The reaction wascontinued until about 400 g of TFE and BuFVE were fed to the autoclave.The autoclave contents were cooled to ambient temperature, vented to 0kPa and discharged as a polymer emulsion. The emulsion was poured into arapidly stirred solution of 50 g magnesium sulfate in 10 l deionizedwater at less than 20° C. to precipitate the polymer. After stirringovernight, the polymer was filtered and washed five times with water at25° C. and then dried at 100° C. under partial vacuum with a sweep ofnitrogen to yield 365 g of a polymer which could be pressed into denseslabs at 120° C. DSC analysis showed a T_(g) at -12.9° C. on the secondheat and no crystalline melting point. Elemental analysis found thefollowing: C, 31.21 wt %; H, 2.24 wt %; F, 61.22 wt %; Br, 0.4 wt %,from which the composition 71.4 mole % CF₂ ═CF₂, 28.0 mole % CF₂═CF--O--C₄ H₉ and 0.6 mole % CH₂ ═CHCF₂ CF₂ Br was calculated.

EXAMPLE 11

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CH₂ ═CHCF₂ CF₂ Br in a 70:30:0.67 mole ratio inaqueous media at 35° C. A 3600 ml horizontal stainless-steel autoclaveequipped with a 4-bladed agitator was charged with 2000 ml deionizedwater, 0.5 g sodium sulfite and 28 g ammonium perfluorooctanoate. Theautoclave was sealed, pressurized with nitrogen to 689 kPa, and thenvented to 0 kPa. This pressure/venting cycle was repeated two times. Theautoclave was evacuated to 0 kPa (absolute) and then purged with CF₂═CF₂ (TFE) to 0 kPa. This evacuation/purge cycle was repeated two times.At 0 kPa of TFE in the autoclave, 0.5 ml CF₂ ═CF--O--C₄ H₉ (BuFVE) and0.5 ml CH₂ ═CHCF₂ CF₂ Br (BTFB) were injected into the autoclave. Theautoclave was agitated at 175 rpm and heated to 30° C. and then chargedwith an additional 207 g TFE, 15.2 ml BuFVE and 1.7 ml BTFB (a 95:5:0.6mole ratio). The pressure reached a maximum of about 2.07 MPa. SolutionA, containing 4 g ammonium persulfate and 4 ml concentrated ammoniumhydroxide per 100 ml deionized water, was injected at 3 ml/min for 9 ml.Concurrently, solution B, containing 4.4 g sodium sulfite per 100 mldeionized water, was injected at 3 ml/min for 9 ml. Solutions A and Bwere then each injected continuously at 0.5 ml/min. After the reactionhad progressed for about 1 hr, the autoclave temperature was increasedto 35° C. The polymerization initiated, a mixture of TFE, BuFVE and BTFBin a 70:30:0.67 mole ratio was fed to the autoclave at about the rate atwhich it was consumed maintaining about 2.07 MPa pressure in theautoclave. The reaction was continued until about 400 g of TFE and BuFVEwere fed to the autoclave. The autoclave contents were cooled to ambienttemperature, vented to 0 kPa and discharged as a polymer emulsion. Theemulsion was poured into a rapidly stirred solution of 75 g magnesiumsulfate in 24 l deionized water at about 50° C. to precipitate thepolymer. The polymer was filtered and washed four times with water atabout 50° C., two times with deionized water at 25° C., and then driedat 100° C. under partial vacuum with a sweep of nitrogen to yield 484 gof a polymer which could be pressed into dense slabs at 125° C. DSCanalysis showed a T_(g) at -12.3° C. on the second heat and nocrystalline melting point. Elemental analysis found the following: C,31.15 wt %; H, 2.01 wt %; F, 63.62 wt %; Br, 0.40 wt %, from which thecomposition 75.0 mole % CF₂ ═CF₂, 24.5 mole % CF₂ ═CF--O--C₄ H₉ and 0.6mole % CH₂ ═CHCF₂ CF₂ Br was calculated.

EXAMPLE 12

This example illustrates the copolymerization of CF₂ ═CF₂, CF₂═CF--O--C₄ H₉ and CH₂ ═CHCF₂ CF₂ Br in a 70:30:0.67 mole ratio inaqueous media at 40° C. A 3600 ml horizontal stainless-steel autoclaveequipped with a 4-bladed agitator was charged with 2000 ml deionizedwater, 0.5 g sodium sulfite and 28 g ammonium perfluorooctanoate. Theautoclave was sealed, pressurized with nitrogen to 689 kPa and thenvented to 0 kPa. This pressure/venting cycle was repeated two times. Theautoclave was evacuated to 0 kPa (absolute) then purged with CF₂ ═CF₂(TFE) to 0 kPa. This evacuation/purge cycle was repeated two times. At 0kPa of TFE in the autoclave, 0.5 ml CF₂ ═CF--O--C₄ H₉ (BuFVE) and 0.5 mlCH₂ ═CHCF₂ CF₂ Br (BTFB) were injected into the autoclave. The autoclavewas agitated at 175 rpm and heated to 40° C. and then charged with anadditional 192 g TFE, 14.1 ml BuFVE and 1.6 ml BTFB (a 95:5:0.6 moleratio). The pressure reached a maximum of about 2.07 MPa. Solution A,containing 4 g ammonium persulfate and 4 ml concentrated ammoniumhydroxide per 100 ml deionized water, was injected at 3 ml/min for 9 ml.Concurrently, solution B, containing 4.4 g sodium sulfite per 100 mldeionized water, was injected at 3 ml/min for 9 ml. Solutions A and Bwere then each injected continuously at 0.5 ml/min. The polymerizationinitiated, a mixture of TFE, BuFVE and BTFB in a 70:30:0.67 mole ratiowas fed to the autoclave at about the rate at which it was consumedmaintaining about 2.07 MPa pressure in the autoclave. The reaction wascontinued until about 404 g of TFE and BuFVE were fed to the autoclave.The autoclave contents were cooled to ambient temperature, vented to 0kPa and discharged as a polymer emulsion. The emulsion was poured into arapidly stirred solution of 75 g magnesium sulfate in 12 l deionizedwater at about 50° C. to precipitate the polymer. The polymer wasfiltered and washed five times with water at about 50° C. and then driedat 100° C. under partial vacuum with a sweep of nitrogen to yield 422 gof a polymer which could be pressed into dense slabs at 120° C. DSCanalysis showed a T_(g) at -11.1° C. on the second heat and nocrystalline melting point. Elemental analysis found the following: C,31.62 wt %; H, 2.16 wt %; F, 60.69 wt %; Br, 0.41 wt %, from which thecomposition 72.0 mole % CF₂ ═CF₂, 27.4 mole % CF₂ ═CF--O--C₄ H₉ and 0.60mole % CH₂ ═CHCF₂ CF₂ Br was calculated.

EXAMPLE 13

This example illustrates the base resistance of polymers preparedaccording to the present invention. Clear solutions of the polymersprepared in Examples 1-7 and 12 were prepared by dissolving 0.5 g ofpolymer in 5 ml hexafluorobenzene. For comparison, a solution of afluoropolymer comprised of hexafluoropropylene and vinylidine fluoride(Viton® E60, available from E. I. du Pont de Nemours and Company, Inc.,Wilmington, Del., U.S.A.) was prepared by dissolving 0.5 g of polymer in5 ml methyl-ethyl ketone. At ambient temperature 1 drop of1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was added to each solution andshaken vigorously for 30 seconds. After treatment with DBU, thesolutions of the polymers of this invention flowed and remained clear ordiscolored only slightly to light yellow. In contrast, after treatmentwith DBU, the solution of Viton® E60 turned an opaque dark amber andgelled to an immobile state. These results demonstrate the excellentbase-resistance of the polymers of this invention. The results for thepolymers corresponding to the following examples are tabulated below.

Example 1--light-yellow, fluid solution; no viscosity increase

Example 2--light-yellow, fluid solution; no viscosity increase

Example 3--clear, fluid solution; no viscosity increase

Example 4--clear, fluid solution; no viscosity increase

Example 5--light-yellow, fluid solution; no viscosity increase

Example 6--clear, fluid solution; no viscosity increase

Example 7--clear, fluid solution; no viscosity increase

Example 12--light-yellow, fluid solution; no viscosity increase

Viton® T60--opaque dark amber solution; immobile gel

What is claimed is:
 1. A polymer which is the product of free radicallycopolymerizing, in the presence of an organic iodide, a reaction mixtureof monomers comprising tetrafluoroethylene, a compound of the formulaCF₂ ═CFOR¹, wherein R¹ is an n-alkyl containing 1 to 6 carbon atoms,and, optionally, other free radically copolymerizable monomers, providedthat:said polymer contains about 0.1 to about 5 percent by weight ofiodine; and repeat unit (I), derived from tetrafluoroethylene, andrepeat unit (II), derived from a compound of the formula CF₂ ═CFOR¹, areat least 50 mole percent of the repeat units of said polymer.
 2. Thepolymer as recited in claim 1 wherein R¹ is ethyl, n-propyl or n-butyl.3. The polymer as recited in claim 2 wherein R¹ is n-butyl.
 4. Thepolymer as recited in claim 1 wherein the molar ratio of (I):(II) isabout 3:1 to about 13:7.
 5. The polymer as recited in claim 1 which alsocontains one or more comonomers selected from the group consisting ofvinylidene fluoride, hexafluoropropylene, and a perfluoro(alkyl vinylether), wherein the alkyl group contains 1 to 5 carbon atoms.
 6. Thepolymer as recited in claim 1 which is an elastomer.
 7. The polymer asrecited in claim 1 which is crosslinked.
 8. The polymer as recited inclaim 1 which consists essentially of repeat units derived from repeatunits derived from tetrafluoroethylene and a compound of the formula CF₂═CFOR¹.
 9. The polymer as recited in claim 1 which contain about 0.5 toabout 2.5 percent by weight iodine.
 10. The polymer as recited in claim1 wherein said organic iodide is selected from the group consisting ofCH₂ I₂, R⁴ I, where R⁴ is a perfluoroalkyl, and I(CH₂ CH₂)_(p) (CF₂)_(m)(CH₂ CH₂)_(p) I, wherein m is 1-10, and each p is independently 0 or 1.11. The polymer as recited in claim 10 wherein m is 2 or 4, and p is 0.12. The polymer as recited in claim 1 which is not crosslinked.
 13. Thepolymer as recited in claim 1 which has been crosslinked by contact withfree radicals.
 14. A polymer comprising the following repeat units:##STR3## and a crosslink-functional repeat unit (III) by means of whichthe polymer is readily crosslinked upon exposure of said polymer to freeradicals;wherein R¹ is an alkyl containing 1 to 6 carbon atoms; providedthat (I)+(II)+(III) are at least about 50 mole percent of the repeatunits in said polymer, and further provided said polymer is notcrosslinked.
 15. A polymer comprising the following repeat units:##STR4## and a crosslink-functional repeat unit (III) by means of whichthe polymer is readily crosslinked upon exposure of said polymer to freeradicals;wherein R¹ is an alkyl containing 1 to 6 carbon atoms; providedthat (I)+(II)+(III) are at least about 50 mole percent of the repeatunits in said polymer, and further provided said polymer has beencrosslinked by contact with free radicals.